1. Field of the Invention
The present invention relates to a hydraulic circuit for an option device of heavy construction equipment which can supply hydraulic fluid from a hydraulic pump to the option device such as a breaker at a constant flow rate, regardless of the size of load produced on the option device, in the case where the option device is mounted on the heavy construction equipment.
More particularly, the present invention relates to a hydraulic circuit for an option device of heavy construction equipment which can facilitate manipulation of the option device such as a breaker and optionally control a flow rate required according to the specifications of the option device by supplying hydraulic fluid from a hydraulic pump to the option device at a constant flow rate, regardless of the size of load produced on the option device.
2. Description of the Prior Art
As shown in FIG. 1, a conventional flow control valve includes a variable displacement hydraulic pump 1, a supply line 8 communicating with the hydraulic pump 1, an option device 2 (e.g., a working device such as a breaker or hammer, a shear, a tilt, and others) connected to the hydraulic pump 1 via an actuator port 7 communicating with the supply line 8, a poppet 5, installed in a parallel path 6, for communicating with the supply line 8 and controlling hydraulic fluid to be supplied to the actuator port 7, and a spool 3, installed in a path between the hydraulic pump 1 and the option device 2, for being shifted in response to a pilot signal applied from an outside to control the flow rate and flow direction of the hydraulic fluid that is supplied to the option device 2.
In the drawing, reference numerals 4 and 4a denote a relief valve.
The hydraulic fluid discharged from the hydraulic pump 1 flows through the supply line 8 to push the poppet 5 upward as shown in the drawing, and is maintained in the parallel path 6. If a pilot signal pressure Pb is applied to the left end of the spool 3 from the outside, the spool 3 is shifted rightward as shown in the drawing. The hydraulic fluid maintained in the parallel path 6 is then supplied to the option device 2 via the actuator port 7 by the spool 3.
The option device 2 has different specifications according to its manufacturer. That is, if various kinds of option devices having different flow rates and pressures are used in the equipment, different flow rates are required for the respective option devices. However, since a constant flow rate is applied from the hydraulic pump 1 to the various kinds of option devices, it is impossible to control the flow rates to the option devices, respectively.
As an operating speed of the option device 2 is varied depending upon the load fluctuation occurring in the option device 2, even a skilled driver cannot effectively manipulate the option device 2, and this causes the workability of expensive heavy construction equipment to be degraded.